FLORHAM PARK, N.J. - Judging from the way he looked on the practice field -- chatting amiably with his players, offering pointers about technique and flashing that trademark smile -- you wouldn't have the slightest clue Rex Ryan might be coaching his last season for the Jets.

Ryan appeared relaxed and confident as he put this year's rookie class of draft choices and free agents through their first NFL workouts, looking like anything but a guy facing an uncertain situation entering his fifth season on the Jets' sideline.

But make no mistake: This is a make-or-break year for Ryan. And if recent history is any indication, Ryan's tenure with the Jets may soon be over.

It's an odd dynamic for the 50-year-old Ryan, who received a vote of confidence from team owner Woody Johnson after last year's 6-10 season but now works with a new general manager who will be the final arbiter of whether the coach stays or goes after 2013. The day Johnson put out his general-manager-for-hire sign after parting ways with Mike Tannenbaum, he made it clear he wanted the head coach to remain. But new GM John Idzik, who has already made his imprint on the team with a sweeping roster overhaul, will ultimately be the one to decide on Ryan's fate.

Take a look at the unusual arrangement in which an incumbent coach works for a new GM, and you'll see the odds are against Ryan. Consider:

The Browns hired Mike Holmgren as team president in 2010, and Holmgren decided to retain head coach Eric Mangini for that season. A year later, Mangini was out, and Holm- gren brought in Pat Shurmur.

And after the 2011 season, the Bears fired longtime GM Jerry Angelo, replacing him with first-time GM Phil Emery. Head coach Lovie Smith was initially retained, but was fired by Emery after just one year.

The one example of success involving a general manager inheriting a coach: the 2007 Giants, who hired Jerry Reese to succeed Ernie Accorsi. Reese and incumbent coach Tom Coughlin won their first of two Super Bowls that year, but the two had already worked closely for several years before Reese, the former personnel director, took over for Accorsi.

So far, Ryan and Idzik have gotten along quite well, and both have been highly complimentary of one another.

But Ryan's long-term tenure remains an open question, because Idzik has no allegiance to him since Ryan wasn't his hire. And as we've seen so far from the first-year general manager, a longtime executive who has earned the respect of his peers at previous stops in Tampa Bay, Arizona and Seattle, Idzik is not afraid to make bold moves.

He made the unpopular -- yet wise -- decision to get a first-round pick and a conditional fourth-rounder for Darrelle Revis, who is coming off a knee injury and would have been nearly impossible to retain on a long-term deal.

Idzik said enough with the Tim Tebow distraction by releasing him two days after the draft.

And Idzik swiftly extricated the Jets from salary-cap purgatory with other moves that at least allowed the team to escape from the financial quagmire he inherited.

What he does with Ryan is now the next big issue for the general manager. Bigger even than what happens with Mark Sanchez, whose play will determine whether this is his final year in New York.

If Ryan shows Idzik that he can navigate the tricky waters of a young and relatively untested roster by remaining competitive in a division that still belongs to Bill Belichick's Patriots, then he'll earn the right to stay. But if the record slips even further after two straight years of regression, then Idzik will no doubt part ways with Ryan and make his own hire.

So don't let Ryan's easygoing manner deceive you now that he begins preparing his team for the difficult slog ahead. It's what happens from September through December that will determine whether the swashbuckling coach gets to stay into 2014.